As the technology nodes shrink in some integrated circuit (IC) designs, the spacing between features continues to decrease. One process for creating conductive features in an active region of a semiconductor substrate includes placing a photoresist mask over the substrate, the photoresist mask is then patterned and etched to form the desired features. A conductive material is then formed in the features.
Metal lines formed in this manner; however, often fail to have the desired shape. For example, a feature designed to have a rectangular shape may have rounded ends and appear more oval upon implementation. The metal line ends can extend into the isolation regions and can contact one another creating a short circuit between adjacent active regions. The short circuit prevents the semiconductor device from functioning as intended.
Critical dimension uniformity (CDU) is a measure of the precision of feature size and shape. For example, when CDU is low, spacing between features must be increased because the chances of one feature being too close to another feature are high. Due to the inability to sufficiently control feature shapes, photoresist masks for conductive line patterns have become increasing complex. The complex mask is more costly to design and produce.
Mask enhancement error factor (MEEF) refers to the degree of pre-correction of a mask to compensate for imaging errors. For example, a mask intended to form rectangular shaped features may not include only vertical and horizontal lines, but also diagonal lines. As the dimensions of the mask decrease, MEEF becomes a major concern because the repositioning of openings begins to dictate the minimum spacing between features.